Certified Photogrammetrist Photogrammetric Data Acquisition — Questions and Answers

Question 1: A frame camera has a 5 µm pixel size and a 100 mm focal length. Flying 2,000 m above terrain, what is the approximate ground sample distance (GSD)?

40 cm
10 cm (Correct answer)
5 cm
20 cm

Correct answer: 10 cm

GSD = pixel size × H / f = 0.000005 m × 2000 m / 0.1 m = 0.10 m.

Question 2: To obtain a photo scale of 1:12,000 with a 152.4 mm focal length camera, what flying height above average terrain is required?

1,524 m
1,829 m (Correct answer)
2,286 m
1,219 m

Correct answer: 1,829 m

H = f × scale denominator = 0.1524 m × 12,000 = 1,828.8 m.

Question 3: Each photo covers 2,000 m on the ground in the flight direction and the plan calls for 60% endlap. What is the air base between exposures?

800 m (Correct answer)
600 m
1,400 m
1,200 m

Correct answer: 800 m

Air base = (1 − 0.60) × 2,000 m = 800 m.

Question 4: An aircraft flies at 60 m/s with a shutter speed of 1/500 s and no forward motion compensation. How far does the ground move during exposure?

0.30 m
0.12 m (Correct answer)
0.03 m
0.06 m

Correct answer: 0.12 m

Ground motion = 60 m/s × 0.002 s = 0.12 m.

Question 5: Why do flight planners typically raise endlap to 80% or more for urban true-orthophoto projects?

To lower the GSD without changing altitude
To reduce the number of flight lines
To minimize occluded areas caused by tall buildings (Correct answer)
To eliminate the need for ground control

Correct answer: To minimize occluded areas caused by tall buildings

Higher overlap provides multiple views of each point so building lean and occlusions can be resolved.

Question 6: Which sun angle condition is generally preferred for aerial photography of terrain to limit long shadows?

Only during civil twilight
Any time the sun is directly behind the aircraft
Sun angle below 15°
Sun angle at least about 30° above the horizon (Correct answer)

Correct answer: Sun angle at least about 30° above the horizon

Specifications commonly require a minimum solar elevation around 30° to limit shadow length.

Question 7: What is the primary purpose of a gyro-stabilized camera mount during image acquisition?

To keep the camera near vertical and compensate for aircraft roll, pitch, and crab (Correct answer)
To cool the sensor during long flights
To synchronize GNSS time with the shutter
To increase sensor dynamic range

Correct answer: To keep the camera near vertical and compensate for aircraft roll, pitch, and crab

Stabilized mounts counter aircraft attitude changes so images stay near vertical and correctly oriented.

Question 8: A 150 m tall tower appears 80 mm from the principal point on a vertical photo taken 1,500 m above the tower's base. What is its relief displacement?

16 mm
4 mm
12 mm
8 mm (Correct answer)

Correct answer: 8 mm

d = r × h / H = 80 mm × 150 / 1,500 = 8 mm.

Question 9: In direct georeferencing, what does the lever arm describe?

The 3D offset vector between the GNSS antenna phase center and the sensor's perspective center (Correct answer)
The distance between the base station and the aircraft
The angular misalignment between IMU and camera axes
The focal length correction from calibration

Correct answer: The 3D offset vector between the GNSS antenna phase center and the sensor's perspective center

The lever arm is the measured spatial offset from the antenna phase center to the sensor reference point.

Question 10: Boresight calibration in an integrated GNSS/IMU camera system determines what?

The small rotational misalignment between the IMU body frame and the camera frame (Correct answer)
Radiometric gain of each band
Antenna phase center variation
Lens distortion coefficients

Correct answer: The small rotational misalignment between the IMU body frame and the camera frame

Boresight angles correct the angular offset between IMU and sensor axes.

Question 11: What is a main advantage of post-processed kinematic (PPK) GNSS over real-time kinematic (RTK) for UAS mapping?

It eliminates the need for an IMU
It requires no base station data
It does not depend on a continuous radio or cellular correction link during flight (Correct answer)
It produces results with no processing

Correct answer: It does not depend on a continuous radio or cellular correction link during flight

PPK applies corrections after the flight, so link dropouts during flight do not degrade results.

Question 12: Under FAA Part 107, what is the general maximum altitude for a small UAS flying a mapping mission away from structures?

1,000 ft AGL
400 ft AGL (Correct answer)
500 ft AGL
200 ft AGL

Correct answer: 400 ft AGL

Part 107 limits operations to 400 ft AGL unless within 400 ft of a structure.

Question 13: Why is airborne GNSS data quality typically degraded during steep banked turns between flight lines?

Base station data is unavailable during turns
Atmospheric delay increases sharply
The IMU switches off during turns
The aircraft wing can block satellites, causing cycle slips and loss of lock (Correct answer)

Correct answer: The aircraft wing can block satellites, causing cycle slips and loss of lock

Banking can mask the antenna from satellites, causing signal loss that must be resolved in processing.

Question 14: A pushbroom (linear array) sensor differs from a frame camera because it:

Builds the image line by line as the platform moves, requiring continuous orientation data (Correct answer)
Requires film processing
Captures the entire scene in a single exposure
Cannot record near-infrared

Correct answer: Builds the image line by line as the platform moves, requiring continuous orientation data

Each pushbroom line has its own exterior orientation, so continuous GNSS/IMU data is essential.

Question 15: A project area is 10 km wide, each image covers 2 km across track, and sidelap is 30%. What is the line spacing?

1.0 km
1.7 km
1.4 km (Correct answer)
0.6 km

Correct answer: 1.4 km

Line spacing = (1 − 0.30) × 2 km = 1.4 km.

Question 16: What is the main effect of a larger base-to-height (B/H) ratio in stereo acquisition?

Lower horizontal accuracy
Improved vertical (height) accuracy but potentially more occlusion (Correct answer)
Smaller GSD
Reduced need for sidelap

Correct answer: Improved vertical (height) accuracy but potentially more occlusion

Wider intersection geometry improves height precision, though it increases viewing differences and occlusions.

Question 17: Crab in aerial photography is caused by:

Lens distortion
Excessive endlap
Failure to correct the camera orientation for aircraft heading drift due to crosswind (Correct answer)
Sun glint on water

Correct answer: Failure to correct the camera orientation for aircraft heading drift due to crosswind

When crosswind makes the aircraft heading differ from its track, an uncorrected camera produces crabbed photos.

Question 18: Which spectral band is most useful for distinguishing healthy vegetation in multispectral acquisition?

Ultraviolet
Blue
Near-infrared (Correct answer)
Thermal infrared

Correct answer: Near-infrared

Healthy leaf structure strongly reflects near-infrared, making NIR key for vegetation analysis.

Question 19: Why does a 12-bit or 14-bit sensor offer an advantage over an 8-bit sensor in aerial imaging?

Faster frame rates
Smaller file sizes
Higher spatial resolution
Greater radiometric resolution to capture detail in shadows and highlights (Correct answer)

Correct answer: Greater radiometric resolution to capture detail in shadows and highlights

More bits per pixel record finer brightness gradations across a wider dynamic range.

Question 20: When terrain elevation varies greatly within a flight line, what happens to GSD and overlap if flying height above sea level is held constant?

Overlap is unaffected, only GSD changes
Over higher terrain, GSD gets smaller and overlap decreases (Correct answer)
Over higher terrain, GSD gets larger and overlap increases
Both remain constant

Correct answer: Over higher terrain, GSD gets smaller and overlap decreases

Higher terrain is closer to the camera, so ground coverage shrinks, reducing GSD and overlap.

Question 21: What is the purpose of a GNSS base station within roughly a limited baseline distance of an airborne mapping project?

To control the aircraft autopilot
To measure atmospheric humidity
To provide differential corrections for precise aircraft trajectory computation (Correct answer)
To trigger the camera shutter

Correct answer: To provide differential corrections for precise aircraft trajectory computation

Short baselines to a base station enable reliable carrier-phase ambiguity resolution for the trajectory.

Certified Photogrammetrist Photogrammetric Data Acquisition

A frame camera has a 5 µm pixel size and a 100 mm focal length.
Flying 2,000 m above terrain, what is the approximate ground sample distance (GSD)?

🃏 Study This Quiz as Flashcards →

📚 Want to go deeper? Read the Full Exam Study Guide →

What Practice Test Geeks adds beyond an AI chat for Certified Photogrammetrist

An AI chatbot can quiz you, but it can't reproduce the exam conditions or keep your record. Here you get:

A timed, full-length Certified Photogrammetrist mock exam — 100 questions in 180 minutes with a 70% pass mark, modeled on the official exam's question count and time limit, followed by a score report broken down by exam domain.
A fixed Certified Photogrammetrist question bank: the same test every attempt, so your score is comparable from one try to the next instead of changing with every regenerated quiz.
Progress saved on your device: completed tests, scores and missed questions stay in My Progress, so you can retake only what you got wrong.
A printable Certified Photogrammetrist cheat sheet you can print or save as a PDF.
Certified Photogrammetrist flashcards built from the same question bank.

Start the Timed Certified Photogrammetrist Mock Exam →

These practice questions were written with AI tools. They are not real exam questions. Exam facts are checked against the official sources listed below. Not reviewed by a subject-matter expert. Editorial policy

Sources & references

Exam facts on this page (fees, format, dates, passing scores) are checked against these official sources; the date is our last check. Editorial policy

asprs.org — Test delivery, eligibility, fees, registration deadline, retake fee, retake policy, score release, time limit, score validity · verified Nov 2026
prometric.com — Registration · verified Nov 2026